Radiation-hardenable resin compositions which are hardened by irradiating with radiations such as ultraviolet rays, electron beams, etc. have been developed for various utilities including printings, paints, electrical insulation, etc. and put into practical uses. The advantages reside in that (1) the compositions are employed in the absence of any solvent and less pollution; (2) the hardening rate is rapid making it possible to quickly reproduce articles; (3) they are hardened as a 100% solid so that a change in volume is extremely small before and after the hardening; (4) there is no thermal loss depending upon material or no thermal influence on material, etc. and, various paints and adhesives for plastics, paper, wood, inorganic materials, etc. have also been developed. Radiation-hardenable paints, inks, adhesives, etc. having such characteristics exhibit excellent properties in adhesion, water resistance, heat resistance, etc.
Epoxy (meth)acrylate resins obtained by ring-opening reacting epoxy resins at the epoxy groups thereof with acrylic acid or methacrylic acid involve various resins including bisphenol A type epoxy (meth)acrylate resins and have been employed for various utilities utilizing the excellent reactivity of the (meth)acrylate group thereof. However, such resins are rigid and brittle. When these resins are used as inks for paper, a crack is caused in the ink when the paper is bent. Further, when utilized as paints on a metal plate such as iron, aluminum, etc., processing for bending of a plate on which the paints are coated results in cracking of the coated layer so that processing is impossible.
By radical polymerization of epoxy (meth)acrylate resins dissolved in styrene using organic peroxides, the resulting polymers are employed for corrosion-resistant FRP and the field relating to resin concretes. Further, by irradiating epoxy (meth)acrylate resins dissolved in a reactive diluent such as styrene or acrylic acid esters with ultraviolet rays or the like in the presence of a sensitizer or by irradiating with electron beams in the absence of any sensitizer, the resins can be hardened in an extremely short period of time and can be used for paints, adhesives, vehicles for printing ink, solder resist inks, relief printing materials, linings for mortar-made floor, coatings for polyvinyl chloride-made tiles, etc.
Although the resins are utilized in many ways, they have various shortcomings such that they are rigid and brittle, have a high viscosity and provide poor workability.